There are currently in excess of 10 million persons in the U.S. that are diabetics; i.e., exhibit an abnormal amount of blood glucose due to bodily misfunction. Many of these persons maintain control through periodic insulin injection, the amount and frequency of which are determined by testing for the blood glucose level. This testing can be in the form of periodic laboratory analysis, such as annual, semi-annual, or more frequent (e.g., daily) testing. The latter usually involves the drawing of blood through the pricking of the person's finger tip. The frequency of testing is dependent upon the sensitivity of the body to the insulin treatment. In severe cases an insulin pump is utilized for accomplishing frequent adjustment of the blood glucose level. Since the glucose level of an individual is not constant, a diabetic is usually given an amount of insulin based upon an average glucose level. Thus, there is a possibility that the patient can receive too little or too much insulin.
In order to reduce the pain of withdrawing blood, as well as potential infection, a non-invasive glucose determination would be desirable. Toward that end there have been certain devices developed for this purpose. For example, a device is described in R. S. Quandt U.S. Pat. No. 3,963,019, issued on June 15, 1976, that utilizes (in one embodiment) a beam of aqueous humor of the patient's eye. The level of glucose present affects the quantity of light exiting the eye, and this can be related to the glucose level. Another non-invasive glucose monitor which involves use of a patient's eye is described in W. F. March U.S. Pat. No. 4,014,321 (also 3,958,560), issued on Mar. 29, 1977. This device determines the optical rotation of polarized radiation as a function of the glucose level. Still other devices for determining the content of a patient's blood are described in N. Kaiser U.S. Pat. No. 4,169,676, issued Oct. 2, 1979; N. C. Ford, Jr. et al. U.S. Pat. No. 4,350,163, issued on Sept. 21, 1982; G. J. Muller U.S. Pat. No. 4,427,889, issued on Jan. 24, 1984; K. Hamaguri U.S. Pat. No. 4,586,513, issued on May 6, 1986; and C. Dahne, et al. U.S. Pat. No. 4,655,225, issued on Apr. 7, 1987. These devices depend upon absorption and/or backscattering of incident radiation to determine glucose levels.
The rotation of polarized radiation as a function of other organic molecules is reported in E. E. Yeung, et al. U.S. Pat. No. 4,498,774 issued on Feb. 12, 1985. The device thereof modulates a polarized laser beam using air gap Faraday rotators. While this device could have applications in the analysis of glucose in blood samples, it is hardly useful for non-invasive glucose analysis. As specified in Column 4 thereof, beginning at line 19, the device occupies a table about 4 feet.times.8 feet. Extreme care must be exercised to prevent vibration. The modulation as used in Yeung is very similar to that employed by one of the present inventors (Hutchinson) in a polarimeter described in "A Modulated Submillimeter-Laser Polarimeter for the Measurement of the Faraday Rotation of a Plasma", Appl. Phys. Letters, 34(3), page 218, Feb. 1, 1979.
Despite the developments made in this field of glucose analysis, none of the known devices have sufficient sensitivity to at all compare with the sensitivity achieved by more rigorous analytical techniques available in laboratories as applied to blood withdrawn from the body. Thus, none are suitable for controlling an insulin pump, for example. In the '321 patent referred to above, while it was previously known that glucose causes an optical rotation of polarized light (as used for sugar content in beers and the like), the degree of rotation caused by glucose levels of the body are extremely small and thus very difficult to measure with any sensitivity. A further drawback to certain of the prior art devices is that the patient's eye is used as the target. Considerable care would have to be exercised using these devices to prevent physical damage of some sort to the eye. Furthermore, insertion of any object in the eye is risky, and must be done carefully. These devices certainly cannot be used without professional help.
Accordingly, it is an object of the present invention to provide a non-invasive apparatus, and method for use of the apparatus, to determine glucose levels in the body with high sensitivity.
It is another object of the present invention to provide for the non-invasive detection of glucose levels without fear of physical damage to the patient.
An additional object of the present invention is to provide a non-invasive instrument for glucose determination that can be utilized by a lay person.
Another object of the present invention is to provide a non-invasive system; and its method of operation, that utilizes the optical rotation of two polarized and modulated orthogonal laser beams for increasing the sensitivity of glucose level detection in a patient.
A further object of the present invention is to provide non-invasive means for determining glucose levels in a patient with sufficient sensitivity such that output signals therefrom can be used to operate an insulin pump whereby the pump supplies only the amount necessary to maintain a desired glucose level.
These and other objects of the present invention will become apparent upon a consideration of the drawings hereinafter in combination with a complete description thereof.